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ASA_CPE 2023.pdf (2.79 MB)

Statewide public health investigation into a multi-facility, multi-species blaNDM-1 plasmid outbreak in Victoria, Australia

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Aim: Describe a genomic and epidemiological investigation of a multi-facility, multi-species blaNDM-1 outbreak in Victoria; and a novel approach to rapid plasmid analysis for real-time surveillance and response.

Background: Historically, blaNDM-1 carbapenemase-producing Enterobacterales (CPE) in Victoria were identified in returned travellers. Between 2019-2021 an increase in patients with blaNDM-1 CPE was detected, many without overseas travel, and several with blaNDM-1 in multiple bacterial species. Frequently, acquisition source was not identified using routine surveillance, prompting an investigation into potential transmission of blaNDM-1 genes on mobile genetic elements.

Methods: All Victorian blaNDM-1 producing isolates collected between January 2012 and October 2021 underwent bespoke genomic investigation to characterise plasmids and identify key antimicrobial resistance (AMR) gene patterns. Epidemiological data, including travel and hospitalisation history, were used to identify epidemiological links.

Results: 183 blaNDM-1 CPE were identified in 114 patients, 47 without known overseas travel. An IncN plasmid carrying 3-4 key AMR genes (mph(A), dfrA14, bleMBL, qnrS1) and blaNDM-1 was identified in 36 patients, accounting for 28/47(59.6%) of patients without known high-risk travel. This plasmid was first retrospectively identified in returned travellers from 2017, and increased notably from July 2020.

Genomic-epidemiological analysis revealed 33/36(91.6%) patients with the outbreak plasmid had admission to two hospitals with 10 different transmission events identified. Suspected ward transmission at a third facility was detected, and overlapping facility-level admissions at four other facilities.

Genomic characterisation of the remaining 19 patients with putative local acquisition, without the blaNDM-1 outbreak plasmid is ongoing.

Conclusion: Identification of a blaNDM-1 plasmid outbreak in Victorian hospitals re-emphasises the importance of screening high-risk patients, and the need for routine methods to detect and respond to plasmid outbreaks to prevent endemicity of imported CPE genes.

Detection and response was enabled by centralised genomic and epidemiological surveillance with embedded translational research partnership, however transmission of carbapenemase genes via mobile genetic elements is inadequately addressed by current surveillance and response protocols. This investigation will inform development of novel approaches to rapidly detect and respond to these events through routine genomic surveillance.

We thank Victorian clinicians, infection control and laboratory staff for their contribution to this work.

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